1. Field of the Invention
This invention relates broadly to interventional cardiology. More particularly, this invention relates to instruments for performing and controlling surgical interventions within the heart.
2. State of the Art
Unlike other organs in the body, the heart is constantly beating, and therefore, constantly in motion. Contractions of the heart wall create severe difficulty in remotely directing the distal end of a laser or other surgical instrument to a desired location, as the heart wall moves with each contraction relative to the apex and distal end. Therefore, when performing less invasive surgical interventions in any chamber of the beating heart it is difficult, if not impossible, to know precisely where the distal end of the instrument is located at any one instant.
There are no known prior art surgical devices which are specifically adapted to compensate for the relative movement of the heart wall of a beating heart during interventional coronary procedures and which permit a cardiologist or surgeon to move the distal end of the instrument with respect to a known location in the beating heart, and thereby discern a relative location of the distal end of the instrument during percutaneous heart surgery.
Percutaneous transmyocardial revascularization (PMR) is becoming an accepted treatment of end stage coronary artery disease and is a procedure in which knowing the relative location of the operating end of a surgical instrument is of paramount importance. A number of companies are developing equipment and procedures to revascularize areas of the heart muscle which have been deprived of adequate circulation because of stenotic disease of the coronary arteries. All known developments use lasers to drill channels in the myocardium, and such first generation devices have shown promise.
In an earlier technology called transmyocardial revascularization (TMR) the chest of a patient was opened and a laser was used to drill multiple holes in the left ventricle under direct observation. Although effective, first generation TMR devices were successful for reasons never envisioned by their developers. TMR was intended to provide a means for permitting blood inside the ventricles to nourish the myocardium via laser drilled channels through the entire ventricular wall. In fact, the laser drilled channels clotted almost immediately. Unpredicted, however, was that new arterial channels developed in or near the laser drilled channels via angiogenesis and supplied limited quantities of oxygenated blood to the adjacent myocardium.
This recent knowledge that TMR operates via angiogenesis suggests that lasers may be suboptimal for initiating the process because of laser induced thermal damage. In addition, lasers are awkward to use in the traditional interventional cardiology procedure room and are expensive. Furthermore, the depth of the drilled channels is difficult to limit with a laser device in PMR procedures. Moreover, manipulation of the laser devices, and other potential drilling tools, is difficult and inexact.